Epitaxial growth apparatus and method of producing epitaxial wafer

ABSTRACT

Provided is an epitaxial growth apparatus which makes it possible to prevent the production of debris between a preheat ring and a lower liner without fracturing the preheat ring. The epitaxial growth apparatus includes: a chamber; an upper liner and a lower liner that are disposed on an inner wall of the chamber; a susceptor being provided inside the chamber; and a preheat ring that is disposed on a supporting portion protruding in an opening of the lower liner and is disposed on the outer circumference of the susceptor. The preheat ring is not supported by the supporting portion in at least a part of a region that is right above a region where the semiconductor wafer passes in a transfer path in which the semiconductor wafer is loaded into the chamber to be set on the susceptor.

TECHNICAL FIELD

This disclosure relates to an epitaxial growth apparatus and a method ofproducing an epitaxial wafer.

BACKGROUND

Epitaxial silicon wafers obtained by forming a silicon epitaxial layeron a silicon wafer, which is a typical semiconductor wafer, have beenused as substrates for fabricating various semiconductor devices such asmetal-oxide-semiconductor field-effect transistors (MOSFETs) and Dynamicrandom-access memories (DRAMs).

FIG. 1 illustrates an example of a single-wafer processing epitaxialgrowth apparatus with which an epitaxial layer is vapor-deposited on asurface of a semiconductor wafer. An epitaxial growth apparatus 100depicted in this diagram has a process chamber 10 having an upper dome11, a lower dome 12, and a dome mounting member 13. The upper dome 11and the lower dome 12 are made of transparent quartz, and are attachedto the dome mounting member 13 with a clamp 14.

An upper liner 15 and a lower liner 16 that have a ring shape and aremade of quarts are disposed on the inner wall of the process chamber 10to protect the dome mounting member 13. A gas inlet 17 for supplyingreactant gas etc. into the process chamber 10 and a gas outlet 18 fordischarging unreacted gas etc. are provided between the upper liner 15and the lower liner 16 on opposite positions in the process chamber 10.

Further, a susceptor 4 on which a semiconductor wafer W is to be set isprovided inside the process chamber 10. The outer circumference of thelower surface of the susceptor 4 is fitted to and supported by susceptorsupporting arms 7 b connected to a main column 7 a of a rotatablesupporting shaft 7, and the susceptor 4 is rotated along with thesusceptor supporting arms 7 b. A base material of the susceptor 4 iscarbon graphite, the surface of which is coated with silicon carbide(SiC), and a counter bore for accommodating the semiconductor wafer W isformed on the surface.

Through holes are formed in the susceptor 4 and the supporting arms 7 b,and lift pins 5 for supporting the back surface of the semiconductorwafer W and elevating the wafer are inserted in the respective throughholes. The lift pins 5 are raised and lowered by vertically movingelevating shafts 6, with the base ends of the lift pins being supportedby the elevating shafts 6.

A ring-shaped preheat ring 60 is disposed on the outer circumference ofthe susceptor 4. The preheat ring 60 preheats reactant gas supplied fromthe gas inlet 17 to the surface of the semiconductor wafer W set on thesusceptor 4. A base material of the preheat ring 60 is carbon graphite,the surface of which is coated with SiC, and the preheat ring 60 issupported by a supporting portion 16 a protruding in the opening of thelower liner 16.

FIG. 2 illustrates the surroundings of a wafer loading port in theepitaxial growth apparatus 100 depicted in FIG. 1. The wafer loadingport is provided in a position deviated by approximately 90° in thecircumferential direction from the positions where the gas inlet 17 andthe gas outlet 18 are provided when the epitaxial growth apparatus 100depicted in FIG. 1 is viewed from above.

As illustrated in FIG. 2, a transfer chamber 20 for transferring thesemiconductor wafer W into the process chamber 10 is provided to beadjacent to the process chamber 10 of the epitaxial growth apparatus100. The transfer chamber 20 and the chamber 10 are communicated via aslit member 21 having a generally rectangular parallelepiped shape.

A communication path 22 allowing for the communication between theinterior of the transfer chamber 20 and the interior of the processchamber 10 is defined in the slit member 21. Further, a slit valve 23for closing the process chamber 10 is provided on the slit member 21 onthe transfer chamber 20 side.

The semiconductor wafer W is set on the susceptor 4 in the followingmanner. First, the susceptor 4 is lowered by the supporting shaft 7.Next, after the slit valve 23 inside the transfer chamber 20 is opened,the semiconductor wafer W placed on a transfer blade B is passed throughthe communication path 22, loaded into the process chamber 10 throughthe wafer loading port 24, and set on the susceptor 4.

Subsequently, the lift pins 5 are raised by the elevating shafts 6 tosupport the back surface of the semiconductor wafer W. After that, thetransfer blade B is retracted from the process chamber 10, and the slitvalve 23 is closed. Further, the susceptor 4 is raised by the supportingshaft 7, the semiconductor wafer W is set on the susceptor 4, thesusceptor 4 is raised to a predetermined height position, and a reactantgas is introduced through the gas inlet port 17 to grow an epitaxiallayer on the surface of the semiconductor wafer W.

When the growth of the epitaxial layer ends and the epitaxial waferobtained is unloaded from the process chamber 10, the above procedure isperformed in the reverse order.

As described above, the preheat ring 60 is supported by the supportingportion 16 a protruding from the lower liner 16; however, the preheatring 60 and the lower liner 16 are made of different materials.Accordingly, when the temperature inside the chamber 10 is increased ordecreased, friction may be produced due to the difference in thecoefficient of thermal expansion between the preheat ring 60 and thesupporting portion 16 a of the lower liner 16, which would result in theproduction of debris of those members, and particles would be depositedon the surface of the semiconductor wafer W.

As semiconductor devices have been increasingly miniaturized andintegrated in recent years, reduction of crystal defects and particlesattached to the wafer surface has been demanded. Accordingly, productionof the debris between the preheat ring 60 and the lower liner 16 asdescribed above are necessarily reduced.

This being the situation, WO 2015/076487 A (PTL 1) discloses a techniqueof preventing the production of debris between a preheat ring and alower liner when the temperature inside a chamber is increased ordecreased, by providing a protrusion under the preheat ring and fixingthe preheat ring to the lower liner.

CITATION LIST Patent Literature

PTL 1: WO 2015/076487 A

SUMMARY Technical Problem

However, in the technique disclosed in PTL 1, when the temperatureinside the chamber is increased or decreased, load caused due to thedifference in coefficient of thermal expansion between the preheat ringand the lower liner is applied, and the preheat ring would be fractured.

To address this problem, it could be helpful to provide an epitaxialgrowth apparatus which makes it possible to prevent the production ofdebris between a preheat ring and a lower liner without fracturing thepreheat ring.

Solution to Problem

We propose the following features to solve the above problem.

[1] An epitaxial growth apparatus used to vapor deposit an epitaxiallayer on a surface of a semiconductor wafer, the epitaxial growthapparatus comprising:

a chamber;

an upper liner and a lower liner that have a ring shape and are disposedon an inner wall of the chamber;

a susceptor on which the semiconductor wafer is to be set, the susceptorbeing provided inside the chamber; and

a preheat ring that is disposed on a supporting portion protruding in anopening of the lower liner and is disposed on an outer circumference ofthe susceptor,

wherein the semiconductor wafer is loaded into the chamber through awafer loading port provided on the chamber with the susceptor beinglowered, and is set on the susceptor after being passed below thesupporting portion of the lower liner and the preheat ring, and

the preheat ring is not supported by the supporting portion in at leasta part of a region that is right above a region where the semiconductorwafer passes in a transfer path in which the semiconductor wafer isloaded into the chamber to be set on the susceptor.

[2] The epitaxial growth apparatus according to [1] above, wherein thesupporting portion is not provided in the at least a part of the region.

[3] The epitaxial growth apparatus according to [1] above, wherein a gapis provided between the preheat ring and the supporting portion in theat least a part of the region.

[4] The epitaxial growth apparatus according to any one of [1] to [3]above, wherein the at least a part of the region is a region in anentire circumference of the supporting portion that corresponds to acentral angle of 10° to 90° with respect to a direction in which thesemiconductor wafer is transferred when the epitaxial growth apparatusis viewed from above.

[5] The epitaxial growth apparatus according to any one of [1] to [4]above, wherein the at least a part of the region is the entire region.

[6] A method of producing an epitaxial wafer, wherein a reactant gas issupplied to the epitaxial growth apparatus according to any one of [1]to [5] above to grow an epitaxial layer on a semiconductor wafer,thereby obtaining an epitaxial wafer.

[7] The method of producing an epitaxial wafer, according to [6] above,wherein the semiconductor wafer is a silicon wafer.

Advantageous Effect

With the above features, the production of debris between a preheat ringand a lower liner can be prevented without fracturing the preheat ring.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings,

FIG. 1 is a schematic view illustrating an example of an epitaxialgrowth device;

FIG. 2 is a schematic view illustrating the structure of a part of anepitaxial growth apparatus in the vicinity of a wafer loading port;

FIGS. 3A and 3B are schematic views of the structure of a part of aconventional epitaxial growth apparatus around a preheat ring, in whichFIG. 3A is a cross-sectional view taken along the wafer transferringdirection, and FIG. 3B is a top view;

FIGS. 4A and 4B are schematic views of an example of the structure of apart of an epitaxial growth apparatus according to this disclosurearound a preheat ring, in which FIG. 4A is a cross-sectional view takenalong the wafer transferring direction, and FIG. 4B is a top view;

FIG. 5 is a schematic view of an example of a lower liner in anepitaxial growth device according to this disclosure;

FIGS. 6A and 6B are schematic views each illustrating another example ofa lower liner in an epitaxial growth device according to thisdisclosure;

FIGS. 7A and 7B are schematic views of still another example of a lowerliner in an epitaxial growth device according to this disclosure;

FIG. 8 is a schematic view of yet another example of a lower liner in anepitaxial growth device according to this disclosure; and

FIG. 9 is a schematic view of another example of a lower liner in anepitaxial growth device according to this disclosure.

DETAILED DESCRIPTION

(Epitaxial Growth Apparatus)

An epitaxial growth apparatus according to this disclosure will now bedescribed with reference to the drawings. An epitaxial growth apparatusaccording to this disclosure is an epitaxial growth apparatus used tovapor deposit an epitaxial layer on a surface of a semiconductor wafer,and includes a chamber; an upper liner and a lower liner that have aring shape and are disposed on an inner wall of the chamber; a susceptoron which the semiconductor wafer is to be set, the susceptor beingprovided inside the chamber; and a preheat ring that is disposed on asupporting portion protruding in an opening of the lower liner and isdisposed on the outer circumference of the susceptor. The semiconductorwafer is loaded into the chamber through a wafer loading port providedon the chamber with the susceptor being lowered, and the semiconductorwafer is set on the susceptor after being passed below the supportingportion of the lower liner and the preheat ring. The preheat ring is notsupported by the supporting portion in at least a part of a region thatis right above a region where the semiconductor wafer passes in atransfer path in which the semiconductor wafer W is loaded into thechamber to be set on the susceptor.

FIGS. 3A and 3B are schematic views of the structure of a part of aconventional epitaxial growth apparatus 100 around a preheat ring 60.FIG. 3A is a cross-sectional view taken along the wafer transferringdirection, and FIG. 3B is a top view. As illustrated in FIG. 3A, theentire circumference of the preheat ring 60 having a ring shape issupported by a supporting portion 16 a of a lower liner 16.

Further, as illustrated in FIG. 3B, a semiconductor wafer W passes belowthe preheat ring 60 in a transfer path in which the semiconductor waferW is loaded through a wafer loading port 24 of the epitaxial growthapparatus 100 to be set on the susceptor 4.

Under these circumstances, when the temperature inside a chamber 10 isincreased or decreased, if debris is produced due to the friction causedbetween the preheat ring 60 and the supporting portion 16 a of the lowerliner 16, particles may be deposited on the surface of the semiconductorwafer W passed below the preheat ring 60.

The inventors of this disclosure diligently studied ways to prevent theproduction of debris that causes the deposition of the particles betweenthe preheat ring 60 and the supporting portion 16 a of the lower liner16. The study led them to conceive a structure in which a preheat ring60 is not supported by a supporting portion 16 a of a lower liner 16 inat least a part of a region that is right above a region where thesemiconductor wafer W passes (hereinafter, may simply be referred to as“semiconductor wafer passing region”) in a transfer path in which thesemiconductor wafer W is loaded through a wafer loading port 24 to beset on a susceptor 4.

FIGS. 4A and 4B are schematic views of an example structure of a part ofan epitaxial growth apparatus according to this disclosure around apreheat ring. FIG. 4A is a cross-sectional view taken along the wafertransferring direction, and FIG. 4B is a top view. In the structuredepicted in FIG. 4A, a preheat ring 60 is configured not to be supportedby a supporting portion 26 a of a lower liner 26 in the entire regionright above a semiconductor wafer W passing region.

FIG. 5 illustrates the lower liner 26 depicted in FIG. 4A. Asillustrated in this diagram, for the lower liner 26, the supportingportion 26 a is not provided in the entire region right above thesemiconductor wafer W passing region. This prevents the production ofdebris between the preheat ring 60 and the supporting portion 26 a ofthe lower liner 26 right above the semiconductor wafer W passing region.For the lower liner 26 depicted in the FIG. 5, the supporting portion 26a is not provided in a region in its entire circumference thatcorresponds to a central angle of ±40° with respect to the transferdirection of the semiconductor wafer W.

With the structure of the supporting portion 26 a of the lower liner 26as described above, as illustrated in FIG. 4B, debris is not producedbetween the preheat ring 60 and the supporting portion 26 a of the lowerliner 26 right above the transfer path while the semiconductor wafer Wis transferred to the top of the susceptor 4, thus the deposition ofparticles on the surface of the semiconductor wafer W can be reduced.

When an epitaxial layer is grown on the surface of the semiconductorwafer W, if polysilicon is deposited between the preheat ring 60 and thelower liner 26, the deposited silicon would fall onto the surface of thesemiconductor wafer W while the semiconductor wafer W is transferred. Inthis regard, the lower liner 26 depicted in FIG. 5 can prevent thedeposition of the polysilicon.

For the lower liner 26 depicted in FIG. 5, the preheat ring 60 is notsupported by the supporting portion 26 a in the entire region rightabove the semiconductor wafer W passing region; alternatively, thepreheat ring 60 may be configured not to be supported by the supportingportion 26 a in only a part or the region.

FIGS. 6A and 6B illustrate other examples of a lower liner in anepitaxial growth device according to this disclosure. For a lower liner36 depicted in FIG. 6A, a ring-shaped supporting portion 36 a is notprovided only in a region in its entire circumference that correspondsto a central angle of ±15° with respect to the transfer direction of thesemiconductor wafer W. Also in such a case, as compared with the case ofusing the conventional lower liner 16 depicted in FIGS. 3A and 3B, theproduction of debris between the preheat ring 60 and the lower liner 36can be reduced, thus the deposition of particles on the surface of asemiconductor wafer W can be reduced. Further, as compared with thelower liner 26 depicted in FIG. 5, sagging (deformation) of the preheatring 60 due to its own weight can be prevented. The above central angleis preferably ±10° to ±90°, more preferably ±10° to ±45°.

Further, for a lower liner 46 depicted in FIG. 6B, a supporting portion46 a is not provided in a region corresponding to a central angle of±40° as in FIG. 5; however, in that region, the supporting portion 46 ais partly provided. This allows the preheat ring 60 to be supported morestably as compared with the case of using the lower liner 26 depicted inFIG. 5.

For the lower liners 26, 36, and 46 depicted in FIGS. 4 to 6B, the partsof the supporting portions 26 a, 36 a, 46 a that do not support thepreheat ring 60 are completely removed when viewed from above, but arenot necessarily configured in this manner.

For example, as in a lower liner 56 depicted in FIGS. 7A and 7B, arecess 56 b may be provided on a surface of a region of a supportingportion 56 a that corresponds to a central angle of ±40° to provide agap between the preheat ring 60 and the supporting portion 56 a. Also inthis case, the production of debris between the preheat ring 60 and thelower liner 56 right above a semiconductor wafer W passing region can beprevented.

Further, a recess(s) may be provided in the supporting portion only in apart of the region above the transfer path as in the lower liners 36 and46 illustrated in FIGS. 6A and 6B. Specifically, for a lower liner 66depicted in the FIG. 8, a recess 66 b is provided in a region in theentire circumference of a ring-shaped supporting portion 66 a thatcorresponds to a central angle of ±15°. Further, for a lower liner 76depicted in FIG. 9, recesses 76 b are discontinuously provided in anarea corresponding to a central angle of ±40° in the supporting portion76 a as in FIGS. 7A and 7B.

Thus, with the structure in which a preheat ring is not supported by asupporting portion of a lower liner in at least a part of a region rightabove a semiconductor wafer passing region, the production of debrisbetween the preheat ring and the supporting portion of the lower linercan be reduced.

As is apparent from the above description, in an epitaxial growthapparatus according to this disclosure, the supporting portion in thelower liner supporting the preheat ring has a characteristic structure,and the other structure is not limited and a conventional structure canbe appropriately used.

(Method of Producing Epitaxial Wafer)

In a method of producing an epitaxial wafer, according to thisdisclosure, a reactant gas is supplied to any one of the epitaxialgrowth apparatuses according to this disclosure that have been describedabove to grow an epitaxial layer on a semiconductor wafer, therebyobtaining an epitaxial wafer.

As described above, in an epitaxial growth apparatus according to thisdisclosure, a preheat ring is not supported by a supporting portion of alower liner in at least a part of a region right above a semiconductorwafer W passing region, thus the production of debris between thepreheat ring and the lower liner can be reduced. Thus, an epitaxialwafer to which reduced particles are attached can be produced bysupplying a reactant gas to the epitaxial growth apparatus according tothis disclosure to form an epitaxial layer on a semiconductor wafer.

The semiconductor wafer which is a substrate of an epitaxial wafer isnot limited; for example, a silicon wafer can be appropriately used, anda silicon epitaxial layer may be appropriately grown on a silicon wafer.The diameter of the semiconductor wafer may be, but not limited to, 150mm or more, specifically 200 mm, 300 mm, 450 mm, etc.

INDUSTRIAL APPLICABILITY

According to this disclosure, the production of debris between a preheatring and a lower liner can be prevented without fracturing the preheatring. Consequently, the epitaxial growth apparatus and the method ofproducing an epitaxial wafer, according to this disclosure are useful inthe semiconductor manufacturing industry

REFERENCE SIGNS LIST

-   -   4: Susceptor    -   5: Lift pin    -   6: Elevating shaft    -   7: Supporting shaft    -   7 a: Main column    -   7 b: Supporting arm    -   10: Process chamber    -   11: Upper dome    -   12: Lower dome    -   13: Dome mounting member    -   14: Clamp    -   15: Upper liner    -   16, 26, 36, 46, 56, 66, 76: Lower liner    -   16 a, 26 a, 36 a, 46 a, 56 a, 66 a, 76 a: Supporting portion    -   17: Gas inlet    -   18: Gas outlet    -   20: Transfer chamber    -   21: Slit member    -   22: Communication path    -   23: Slit valve    -   24: Wafer loading port    -   56 b, 66 b, 76 b: Recess    -   60: Preheat ring    -   100: Epitaxial growth apparatus    -   B: Transfer blade    -   W: Semiconductor wafer

1. An epitaxial growth apparatus used to vapor deposit an epitaxiallayer on a surface of a semiconductor wafer, the epitaxial growthapparatus comprising: a chamber; an upper liner and a lower liner thathave a ring shape and are disposed on an inner wall of the chamber; asusceptor on which the semiconductor wafer is to be set, the susceptorbeing provided inside the chamber; and a preheat ring that is disposedon a supporting portion protruding in an opening of the lower liner andis disposed on an outer circumference of the susceptor, wherein thesemiconductor wafer is loaded into the chamber through a wafer loadingport provided on the chamber with the susceptor being lowered, and isset on the susceptor after being passed below the supporting portion ofthe lower liner and the preheat ring, and the preheat ring is notsupported by the supporting portion in at least a part of a region thatis right above a region where the semiconductor wafer passes in atransfer path in which the semiconductor wafer is loaded into thechamber to be set on the susceptor.
 2. The epitaxial growth apparatusaccording to claim 1, wherein the supporting portion is not provided inthe at least a part of the region.
 3. The epitaxial growth apparatusaccording to claim 1, wherein a gap is provided between the preheat ringand the supporting portion in the at least a part of the region.
 4. Theepitaxial growth apparatus according to claim 1, wherein the at least apart of the region is a region in an entire circumference of thesupporting portion that corresponds to a central angle of 10° to 90°with respect to a direction in which the semiconductor wafer istransferred when the epitaxial growth apparatus is viewed from above. 5.The epitaxial growth apparatus according to claim 1, wherein the atleast a part of the region is the entire region.
 6. A method ofproducing an epitaxial wafer, wherein a reactant gas is supplied to theepitaxial growth apparatus according to claim 1 to grow an epitaxiallayer on a semiconductor wafer, thereby obtaining an epitaxial wafer. 7.The method of producing an epitaxial wafer, according to claim 6,wherein the semiconductor wafer is a silicon wafer.
 8. The epitaxialgrowth apparatus according to claim 2, wherein the at least a part ofthe region is a region in an entire circumference of the supportingportion that corresponds to a central angle of 10° to 90° with respectto a direction in which the semiconductor wafer is transferred when theepitaxial growth apparatus is viewed from above.
 9. The epitaxial growthapparatus according to claim 3, wherein the at least a part of theregion is a region in an entire circumference of the supporting portionthat corresponds to a central angle of 10° to 90° with respect to adirection in which the semiconductor wafer is transferred when theepitaxial growth apparatus is viewed from above.
 10. The epitaxialgrowth apparatus according to claim 2, wherein the at least a part ofthe region is the entire region.
 11. The epitaxial growth apparatusaccording to claim 3, wherein the at least a part of the region is theentire region.
 12. The epitaxial growth apparatus according to claim 4,wherein the at least a part of the region is the entire region.
 13. Amethod of producing an epitaxial wafer, wherein a reactant gas issupplied to the epitaxial growth apparatus according to claim 2 to growan epitaxial layer on a semiconductor wafer, thereby obtaining anepitaxial wafer.
 14. A method of producing an epitaxial wafer, wherein areactant gas is supplied to the epitaxial growth apparatus according toclaim 3 to grow an epitaxial layer on a semiconductor wafer, therebyobtaining an epitaxial wafer.
 15. A method of producing an epitaxialwafer, wherein a reactant gas is supplied to the epitaxial growthapparatus according to claim 4 to grow an epitaxial layer on asemiconductor wafer, thereby obtaining an epitaxial wafer.
 16. A methodof producing an epitaxial wafer, wherein a reactant gas is supplied tothe epitaxial growth apparatus according to claim 5 to grow an epitaxiallayer on a semiconductor wafer, thereby obtaining an epitaxial wafer.